Re: myth of warped disks

According to you, a "wobble" isn't warpage.

Define warpage. You cannot say it does not exist if you cannot define it.

I've defined it, and measured it, yet you say it does not exist.

Vic Smith wrote, on Tue, 04 Nov 2014 22:44:06 -0600:

I've had this discussion so many times, I know exactly how it goes.

There are a few more steps, but, the step is always said by those who insist that their rotors warped (even though absolutely

*none* of them actually measured, and most don't even know *what* to measure, nor how) that they meant the word differently.

You'll notice in my initial posts, I was *very clear* about what "I" meant by "warp".

So, those who insist their rotors "warped", change the definition, which, is fine (I've seen this happen every time).

There are still a few more stages to go through, but, we cannot proceed until people read what the experts have to say. It matters not what "I" have to say. Read the links found by the Google search.

Note: If folks actually read those links, we'd proceed to the next stage, which is that they'd see that even the experts don't agree on all points - so then we go down the semantics road again - but we aren't there yet... :)

clare wrote, on Tue, 04 Nov 2014 23:14:29 -0500:

Ok. Show me a picture of the measurements on a street-use rotor.

(I've been asking this question for at least a decade, and *nobody* has ever provided a picture of them measuring warp on street-use rotors, mainly because they didn't measure them.)

They're all just guessing.

The best we ever get is a measurement of runout.

Watch and see. (I've been down this road scores of times before...)

nestork wrote, on Wed, 05 Nov 2014 06:32:23 +0100:

What I go by are the ratings of my brake pads, which, as you all know, is required printing on all passenger vehicle pads sold in the USA.

I would never put in anything less than FF, for example, for the cold/hot friction ratings. Maybe even GG, if I get them for a good price.

And, yes, I've been down the argument that the government mandated friction ratings don't test the real world - but it beats marketing innuendo (ceramic and all that hogwash notwithstanding).

clare wrote, on Tue, 04 Nov 2014 23:19:23 -0500:

You didn't read a single one of the references. And, you're changing the definition.

I was *very clear* on my definition. Runout is runout; it isn't warp (as in potato chip).

But, don't believe me. Read what the experts have to say.

clare wrote, on Tue, 04 Nov 2014 23:23:20 -0500:

Same way you measure warp for an engine block.

Danny D. wrote, on Wed, 05 Nov 2014 07:25:02 +0000:

Here are some found by that simple google search ...

Police care about rotor warp, right?

Professional car tech bloggers care about rotor warp, right? Companies that sell brake components care about rotor warp, right? Car enthusiasts care about rotor warp, right? Braking enthusiasts care about rotor warp, right? How about the Raybestos brake tech school? Of course, then there are the people who say one thing, and then another: But, overall, the evidence is pretty clear (although, as I said, I've read every single article there is on this, and they don't all agree).

Note: I'm positive you'll find articles that "assume" rotor warp, as I've been down this road many times. However, in *every* one of those cases, what you *won't* see is a balanced discussion of the argument that rotors don't typically warp. You'll quickly notice that those who say rotors don't warp *know* all about the counter argument, while those who say rotors warp invariably are clueless about the counter argument.

And, nobody who says their street rotors warped ever measured it and proved that they did (they all *say* they did, but none can provide a picture).

Vic Smith wrote, on Tue, 04 Nov 2014 22:44:06 -0600:

Look at my very first post on this subject ...

The main reason for *understanding* what is going on is *not* to solve the short-term problem (which is always to replace or machine or rebed or retorque the rotors for all rotor-specific DTV/BTV/runout problems).

The main reason for understanding what is really going on is to formulate the correct *long term* solution.

If you think your street rotors warped (like a potato chip), then you will implement the wrong long-term solution, but the right short-term solution.

I've been down this road so many times, I know where we are going, but you have to read what the experts have to say.

Bear in mind, they don't all agree on all topics, and also bear in mind you will certainly find articles that state that true warp actually exists - but - you'll *never* find an article that says that, while acknowledging that the counter argument exists.

Whereas, you'll *always* find the counter argument explained in all the threads from experts who say it's a myth that street rotors commonly warp.

It's just like people saying you'll catch cold if you go outside without a hat and coat on in the freezing rain. You won't, and you can't - but they'll never believe it ... but those who know how you catch cold know BOTH SIDES of the argument while those who insist they caught cold in the cold, don't even UNDERSTAND the other side of the argument.

Same thing with warp. Lack of understanding is the problem. Until that's fixed, you can't come up with the correct long-term solution to the problem.

Danny D. wrote, on Wed, 05 Nov 2014 07:55:59 +0000:

This is the key!

Everyone thinks they're a diagnostic genius when they replace rotors and their "warp" magically instantly goes away.

Yet, they start to complain about the car's brakes when the warp comes back, over time.

They don't realize, most of the time, THEY are the reason.

The short term problem is the same, whether it's really a warped rotor or if the rotor has simple DTV, for example.

But, the long-term solution is totally different - but you can't get there, until you understand what caused the vibration in the first place.

And, it wasn't warp (as in potato chip).

Thanks. I'l give your tips a try. I have noticed that the oscillation is not always there, so your explanations make sense.

I have measured warp on street-use rotors, but that warp was a _consequence_ of some other problem. People drive around with bad steering bushings, they get severe shimmy, and when they get that shimmy on braking it causes uneven rotor wear, etc.

So, I'd say you're kind of correct and kind of incorrect.

--scott

Hi, Don't believe rotor disc can be warped? Days when they used cast rotor, warp story was never around. To reduce weight(?) they started using light weight rotor. When lug nuts were over tightened, things started happening. Now every one pays attention to lug nut torque.

Scott Dorsey wrote, on Wed, 05 Nov 2014 08:01:56 -0500:

It's not "me", it's the record.

However, it begs the question.

How did you measure this warp?

Mayayana wrote, on Wed, 05 Nov 2014 07:54:13 -0500:

As you rebed the brakes the pad deposits can change, and what oftne happens is that the "character" of the vibration changes (either the speed at which it starts and stops, or severity, or whatever).

That's a good clue that you're dealing with deposition and not some mechanically different problem, such as warp.

Rebedding would *never* change the character of warp. Rebedding *often* changes the character of what people "call" warp.

The long term solution is different when there's real warp involved from when it's merely DTV or BTV due to uneven pad deposition.

Good luck. Let us know how it works out. Once you understand this beast, you can drive with more finesse on the brakes.

Mike wrote, on Wed, 05 Nov 2014 09:20:59 -0500:

Nobody is saying that except you.

Specifically, we provided a ton of good references, and we all know you can find hundreds of thousands of Internet references where people actually think their street rotors warped.

You're the only one saying that it's true because YOU read it on the net.

Danny D. wrote, on Wed, 05 Nov 2014 19:05:00 +0000:

I apologize for my tone. It bothered me that Mike took things wholly out of context, but, I should have simply ignored the post.

I apologize for not being civil.

With a dial indicator of course. Although the sort of problem caused by uneven wear can be detected even with a micrometer because the thickness varies.

--scott

We ALL know a cold is caused by a virus - but what experts like you forget is that virus is always around - and in most cases it does not make you sick because yourimune system fights it off. One way your body kills virii is by the use of HEAT. That's what a fever is from - your body fighting off an invader.

Lowering your body temoerature can reduce your body's ability to fight off the infection - thereby CAUSING you to CATCH a cold.

Does the cold temperature and wet CAUSE the cold???? Nope. But that does not mean going out in the cold and wet without a hat and cold is a smart move and will not increase the likelihood of you catching a cold????? Only a fool believes that.

The only long term solution to genuinely warped rotors is to use high quality, well engineered parts and don't overheat them. Not overheating them requires proper service and maintenance and proper driving habits.

Poor quality parts, insufficient maintenance, OR bad driving habits CAN cause genuine warping - as well as the problems you insist are the ONLY common and misdiagnosed cause of brake pulsations generally referred to as "warped rotors"

You still do not know the definition of warp. Warpage is distortion of the shape of the rotor from external (and usually thermal) forces. Doesn't matter if it is "classic" potato chip, "ruffles" or what you call "run-out". What defines warpage is what causes it. Warpage does NOT include material deposit or wear, or corrosion damage.

Distortion from heat DOES happen on street driven vehicles - and it is much more common on a vehicle after the rotors have been cut to "correct" "warpage" by any definition because cutting the rotor reduces it's thermal mass, it's stiffness, and therefore it's resistance to overheating and warpage.

It is also more common a vehicles towing a trailer or otherwize operating under higher than normal load conditions or higher speeds.